In the past, many different types of bearings were utilized to journal a rotatable assembly of a dynamoelectric machine, and many different schemes were employed to transmit to such bearings a thrust force engendered in response to the rotation of the rotatable assembly when the dynamoelectric machine was energized across a power source.
To avoid the obvious disadvantageous or undesirable feature of the cost involved in employing ball or roller bearings in a dynamoelectric machine, many of the past dynamoelectric machines utilized a sliding type of bearing, such as a generally tubular sleeve bearing or self-aligning bearing for instance, when the duty or application of such past dynamoelectric machines was conducive to the use of such sliding type bearing. However, it is believed that a simple, low cost, dependable and durable sliding type bearing which both journals and takes the thrust of a rotatable assembly in a dynamoelectric machine is difficult to achieve, particularly if the lubricant supply or feed to such sliding type bearing is by lubricant wicking means rather than by a pressurized lubricant source.
In order to overcome the aforementioned disadvantageous or undesirable feature involving wick feeding of lubricant to the past sliding type bearing, many of such sliding type bearings were formed of a compressed powder material, such as a sintered powder metal or the like for instance. Of course, the sintered powder metal of these past sliding type bearings was somewhat porous having interstices therein generally defining capillary lubricant flow passages or capillary paths through such bearings communicating with all of the surfaces thereof. Thus, with respect to lightly loaded surfaces or interfaces of the past sintered powder metal bearing, such as a bore or journaling surface thereof for instance, lubricant exuded or flowed from the capillary paths in such bearing so as to lubricate such lightly loaded surface or interface. Further, if the porosity of the past sintered powder metal bearing was considerable, lubricant may have been stored therein. However, it is believed the sintered powder metal bearing has a serious disadvantageous or undesirable feature when a surface thereof is subjected to high loading forces. For instance, while the capillary paths permitted the egress therefrom of lubricant, as discussed above, lubricant also ingressed into the capillary paths; therefore, when a surface of the sintered powder metal bearing was highly loaded, i.e., in thrust transfer engagement with a thrust collar or the like for instance, any lubricant on such highly loaded surface may have been forced therefrom into the capillary paths communicating with such surface due to the thrust transfer engagement thereby to obviate the possibility of establishing at least a partial hydrodynamic film of lubricant between the highly loaded surface and the thrust collar.
In some of the past sintered powder metal sliding type bearings, the surfaces thereof subjected to high load were treated in order to completely close the capillary paths communicating with such highly loaded surfaces. For instance, it is well known to the art to infiltrate these high load surfaces with a fluid, such as a liquid resin or a molten metal or the like, with such fluid penetrating and solidifying in the capillary paths of the bearing communicating with such high load surfaces thereby to completely close such capillary paths and obviate lubricant ingress and egress therethrough. With the capillary paths closed, as discussed above, it is, of course, then possible to establish a hydrodynamic film of lubricant between the high load surface and the aforementioned thrust collar associated in thrust transfer relation therewith. However, one of the disadvantageous or undesirable features of this above discussed fluid method of closing capillary paths to the highly loaded surface is believed to be that such method may have been somewhat slow and laborious thereby increasing production costs. Another disadvantageous or undesirable feature of this above discussed method is believed to be that the application of the liquid resin or molten metal to the high load surface of the bearing may have been rather messy in a production area and may have involved hazardous working conditions in such production area.